Yarn unevenness tester



YARN UNEVENNESS TESTER Filed July 1, 1950 JNVENTOR. JOSEPH A. TRU/TT ATTORNEY- Patented Mar. 2, 1954 YARN UNEVENNESS TESTER Joseph A. Truitt, West Chester, Pa., assignor to American Viscose Corporation, Wilmington, Del., a corporation of Delaware Application July 1, 1950, Serial No. 171,653

paratus for testing yarns, filaments, and the like.

More particularly the invention relates to a method and apparatus for testing the unevenness, particularly the unevenness in the distribution of the mass per unit length which is commonly called linear density, of a continuously moving thread, yarn, filament, or the like. The present invention is applicable to the testing of any type yarn, thread, filament, roving, or the like, for example those formed from silk, cotton, wool, hemp, flax; artificial filaments and fibers, such as from cellulose esters and ethers, viscose, cuprammonium cellulose; wire, glass, casein, vinyl resins, and other synthetic materials such as'nylon, and the like, etc. The invention is particularly applicable to the testing of continuous filament yarns formed from suitable above-mentioned materials.

As used throughout the specification and claims, yarn is intended to include all types of strands, filaments, threads, yarns, and the like, whether of the continuous filament or spun type. In a fabric formed from spun yarn, rather large changes of random distribution in the H yarn are objectionable because the appearance of fabric when made of synthetic or rayon yarns, for example, is of utmost importance since the .more level the fabric surface, the more objectionable and noticeable will be variations of yarn thickness.

The known and standard methods for the measurement of silk and rayon yarn are not too satisfactory since they are tedious, wasteful of yarn, and inaccurate. Since the yarn has the characteristics of a loosely twisted rope, it is not truly round at any point in its length. The diameter and linear density varies continuously from the average diameter throughout its length.

One known method of measuring this unevenness in linear density of yarn is to weigh consecutive samples of the yarn which have been cut in short pieces of known and equal length, and then chart these weights in curve iorm to show the progressive linear density .changes for the lengths measured. The dis- 7 Claims. (01. 324-61) 2 advantages attendant a method of this kind will be obvious to those skilled in the art.

Various electrical devices are known for measuring the thickness or mass of stationary or continuously moving yarns or sheets, for example, those in which the yarn or sheet is guided or led through a light beam or an electronic pick-up element and the variations in thickness or weight are recorded automatically and continuously. However, these electrical devices have not proved entirely satisfactory for the continuous measurement of the unevenness in linear density of regular twist continuous filament yarns for various reasons, the principal among which are: (1) regular continuous filament yarns are normally spun in the primary manufacturing operation with low or zero twist; (2) low twist, or lack of twist, produces a nonuniform silhouette or unevenness of form when the yarn is guided through a light beam or an electronic pick-up element, i. e. since the yarn under tension assumes a ribbon-like form, it will present flats and edges of irregular length and disposition as it passes through the detection area. Flats refer to the face or wide surface and edges refer to the narrow surfaces of the uneven yarn; and (3) these means measure this unevenness of form or silhouette in addition to linear density variations, thus masking the latter desired measure;

However, it has now been found that the unevenness in linear density of regular twist continuous filament yarns may be accurately measured,

and reproducible results obtained, without form factor alterations, i. e., without measuring the unevenness of form in addition to linear density variations.

Accordingly, it is a primary object of the present invention to provide a method and apparatus for measuring continuously the unevenness in linear density of a continuously moving yarn.

" Another object of the invention is to provide a method and apparatus for measuring the unevenness in linear density of regular twist continuous filament yarns.

Another object of the invention is to eliminate or reduce the effects of unevenness of form measurements so that conventional equipment of photocell scanning and electronic capacitance types may be used with the accuracy desired for unevenness in linear density measurement of continuous filament yarns.

It is another object of this invention to provide a method and apparatus for measuring the unevenness in linear density of spun yarns and In general the objects of the present invention i are accomplished by continuously passing a yarn to be tested along a path and measuring :or 'detecing the linear density of the yarn at .a point along the path while at the same time twisting the yarn by rotating the same on its axis, 1. e., by rotating a portion .of the yarn 'on its axis be- ,yond the point of detection of linear density rel- .ative to a portion of the yarn preceding and advancing to the point of detection. In this way an essentially constant and increased number of flats and edges are maintained within the pickup area. By maintainingan essentially constant number of flats and edges in the pick-up or detection area, unevenness or variations due to the form of the material being tested are alleviated and the recorded data, obtained, for example, by change in capacitance of .a condenser as the yarn :is passed between the plates of the same, is an approximately true picture of .the linear density of the yarn tested, or or" the variation in thickness of the yarn, depending upon how the results are interpreted.

Linear density, as used throughout this-specificattion and the appendedclaims, is intended to mean, broadly, the weight per unit length of yarn or thread. Because .of the fact that filaments made from different materials have different densities the best results are obtained when the yarn being tested is made from filaments which are all alike, for example .a yarn made entirely of viscose rayon filaments. Mixed filament yarns may be tested by means of the present invention but in the case of spun yarns, it is important that the composition of the yarn be known in order that the recorded results may beintelligentlyinterpreted.

The essential feature of the present invention is to twist the yarn or thread as the samepasses between the condenser plates or any other @type linear density detection or measuring device, :by

rotating the yarn on its axis. It is preferable that the yarn does not touch either condenser "plate with sufiicient pressure to prevent the 'full amount of twist passing through the pick-up element. This twisting of the loose-twist continuous filament yarns alleviates variations or "unevenness due to form and results in an accurate measurement of the linear density or yarn weight. The diameter of the yarn is proportional to the weight and a large diameter in the low twist yarn will still show up as such after the yarn is twisted. Therefore, twisting does not .afifect the accurate measurement of the linear density of the yarn and the results obtained are proportionally a true picture of the yarn in an untwisted state.

In order that the following detailed description may 'be more clearly understood reference should be had to the accompanying drawing which is merely intended to be illustrative and not limitative and in which- Figure 1 represents a diagrammatic view of the invention as the same is employed with an electronic capacitance type measuring or testing device, and

Figure 2 is a diagrammatic view of the inven tion as it is employed in connection with a testing device of the photocell scanning type.

Referring to Figure 1, the yarn 3 to be tested is unwound from the yarn package 4 and fed through the testing device by means of feed rollers 5. .As the yarn is unwound from the package '4, .it passes .tlntough a guide 6 and over a guide roller 1. Ifhe yarn then proceeds downwardly over a V-shaped guide 8, then between the condenser plates 9 and Iii, through guide II, which serves to prevent ballooning of the yarn as it is twisted, through the false twister i 2, and then through feed rollers 5 and guide .13 to a suitable container or winding device, not shown.

The false twister is driven or rotated by moto ld'by means of pulleys l5 and i6 and belt .I] connecting the same. The twister comprises a tube [8 through which the yarn passes and emerges through the opening [9 adjacent the bottom thereof. While a false twister has been shown, the invention is equmly operative with any of the usual and known type .twisters, for example, the yarn may pass through the linear density measuring device as it proceeds to a take-up twister, such as a cap twister, fiyer twister, ring twister, and the like. .The invention is also equally operative with any type .of false twister, such as those using jaws, rotating rings, .or 13111- leys, etc. The twist is put into the yarn between the opening 19 and the guide 8. In like manner, the twist is taken out :of the yarn between the opening [9 and feed rollers 5. Thus when the yarn is rewound, it is substantially inits original condition of twist. When testing low denier yarns, such as 10-15 denier, the tube [:8 of the false twister should have an opening in the center thereof and concentric with the axis of the same, which is only slightly greater in diameter than the low denier yarn. In addition the guide All may be so constructed that it is capable of being rotated in the same direction that the yarn is rotated. These variations tend to assist in prevention of yarn ballooning and also prevent the yarn from coming in contact with the .condenser plates, and assure that the twist goes back through the measuring zone.

The condenser plates 9 and H! are preferably made of non-conductive material having conductive inserts or measuring elements 28 and 21 therein which in turn are connected to the electronic circuit (not shown) which is contained in a suitable housing 22, by lines 23 and 2'4. Lines 25 and 23 connect the electronic circuit to the recorder 21 and lines 28 and 29 connect the circuit to motor 30 which in turn drives the continuous recorder 21.

The measurement of the weight per unit length of yarn or the linear density is accomplished by measuring the change in capacity of a condenser which is hooked up "to an electronic circuit and automatic recorder. When substances having a different dielectric constant from that of air are introduced between the plates of a condenser, the capacity thereof changes dependent upon the dielectric constant, the amount of material introduced, and its shape and form. When the substance introduced is a relatively loose material, such as a'yarn, the capacity. of the con-' denser is directly proportional to the weight of the material between the condenser plates and it can be taken as linear.

Since the dielectric constant of a fiber or filament is greatly influenced by moisture content, it is preferable to condition samples to be tested, and then test the same, in a room of controlled humidity and temperature.

The electronic circuit, which is not the novel feature of the invention, has not been shown in order to simplify the description of the invention. Any of the known yarn testing devices employing such a circuit may be employed in the present invention. For example, among the suitable testing devices may be mentioned the Uster device produced by Zellweger AG. of Switzerland, or the Uniformity Analyzer of the Brush Development Company. A suitable electronic photocell scanning device is the Serc Electron lt Iicrometer produced by the Standard Electronic Research Corp.

While the details of the electronic circuit have not been shown, in principle the operation of the same is generally as follows: the amplified signal from a high frequency oscillator is employed to generate a voltage across the tuned grid circuit of a detector. The grid circuit is detuned from peak resonance so that a linear portion of the tuning curve is used. The capacity of the measuring condenser, between the plates of which the yarn being tested is passed, determines the voltage generated. The detector output voltage is recorded on the chart of the continuous recorder 21 and since this detector output voltage is proportional to the voltage generated in the tuned grid circuit, it is a record of the change in weight of the yarn passing between the plates of the measuring condenser. As the yarn is drawn through the measuring condenser, the recorder indicates directly the weight of the yarn between the condenser plates at any instant.

The space between the condenser plates 9 and It may be varied depending upon the size of the yarn being tested.

While the apparatus is shown with the yarn traveling in a vertical direction, it may also be arranged with the yarn traveling horizontally.

The embodiment, shown diagrammatically in Figure 2, is essentially the same as that in Figure 1, except that in place cf the condenser plates 9 and it there is employed a light source 3!, a prism 52, through which the light beam passes to a photocell 33. The yarn 3 passes through the light beam which is comprised of parallel rays of light. The light source and photocell are connected to an electronic circuit (not shown) similar to that employed in connection with the electronic condenser.

The speed with which the yarn is passed through the testing device may be varied in accordance with the type yarn being tested and the type chart desired. The speed of the chart may also be varied independently of the speed of the yarn. The higher the chart speed, the more exacting the analysis of the linear density obtained. For example, the yarn speed may vary from 1 to 300 yds./minute and the chart speed may vary from 1 to 125 mm./second. The amount of twist put in the yarn will vary with the size and initial twist of the yarn. For example, 150 denier yarns, originally 0-5 turns/inch, have 15-30 turns/inch, 190 denier yarn, originally having 0-5 turns/inch may have 20'-6O turns/inch, and 75 denier yarn originally having .0- turns/inch may have 20-70 turns/inch.

' All filaments and yarns are produced in standard sizes to have a certain weight or linear density. The charts are so arranged that they show a plus or minus deviation from a mean linear density. The known instruments, above referred to, are capable of being set on a mean or zero reading prior to the beginning of the test. Thus, by knowing the ratio of yarn speed to chart speed, the chart shows a true picture of the linear density or weight per unit length of the yarn tested. Further, the mean weight of the yarn tested is easily determined. The charts are divided into unit sections of equal length. A distance greater than the shortest predominant'irregularity cycle is chosen and an average of the maximum and minimum readings in each section taken. These values are in turn averaged over the whole record and this over-all average is a close estimate of the mean weight of the yarn tested.

The present invention provides a means of employing standard yarn unevenness testers for the measurement of the linear density of regular twist continuous filament yarns without the variations in the yarn due to form influencing the true values desired. The apparatus is especially useful in plant control Work and may be employed in conjunction with conventional twisting spindles. Spun yarns and rovings in which deformation of shape occurs, such as in packaging, may conveniently be tested by means of the present invention which alleviates the form variations due to package deformation from masking the true values of linear density or weight. Numerous other advantages will be obvious to those skilled in the art.

It is of course to be understood that changes and variations may be made without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. An apparatus for measuring the unevenness in linear density of yarns comprising condenser plates connected to an electronic circuit, means for passing the yarn between the condenser plates, twisting means for twisting-the yarn between the condenser plates, yarn guide means between the condenser plates and twisting means for preventing the ballooning of the yarn, and recording means connected to the electronic means.

2. An apparatus for measuring the unevenness in linear density of yarns as defined in claim 1 wherein the twisting means comprises means for rotating a portion of the yarn on its axis beyond the linear density measuring means relative to a portion of the yarn preceding the linear density measuring means.

3. An apparatus for measuring the unevenness in linear density of yarns as defined in claim 1 wherein the twisting means comprises a false twister.

4. An apparatus for measuring the unevenness in linear density of yarns comprising linear density measuring means comprising an electrical condenser, means for guiding the yarn through the field of the condenser, and means for twisting the yarn as it passes through the field.

5. In a process for measuring the linear variation in the weight per unit length of a yarn by measuring the influence of the yarn on the capacitance of an electrical condenser and by dispcs'mg successive linear sections of the yam within a region wherein the yeah effects said capacitance by relative movement between the yarn and the condenser in the lengthwise directions of the yarn, the step of twisting said -sections of the yam as they become disposed within said region through approximately an equal number of turns per unit length to substantially eliminate variations which occur in the cross-sectional form of such sections before the sections are subjected to said twisting step.

43. in a process for measuring the linear variation in weight per unit length of a yarn by measuring the influence of the yarn on the capacitance of an electrical condenser and by passing the yarn along a path extending through a region wherein the yarn effects the capacitance, the step of twisting successive sections of the yarn as they pass through said region through approximately an equal number of turns per unit '8 length to eliminate the variations which occur in the cross-sectional form of such sections before the sections are subjected to said twisting step.

'7. A process as defined in claim 6 wherein the yarn is passed relative to the region in continuous movement and the yarn is continuously twisted about its longitudinal axis by rotation to incorporate a false twist in the section thereo! disposed in said region.

JOSEPH A. TRUITI.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Re. 23,368 Grob et all May 22, 1951 1,838,682 Ingham Dec. 29, 1931 1,984,166 Walter Dec. 11, 1934 2,524,936 Smith Oct. 10, 1950 

